Periodically the glacier advances over the L-shaped lake Lago Argentino forming a natural dam which separates the two halves of the lake when it reaches the opposite shore. With no escape route, the water-level on the Brazo Rico side of the lake can rise by up to 30 meters above the level of the main lake. The enormous pressure produced by the height of the dammed water finally breaks the ice barrier holding it back, in a spectacular rupture event. This rupture cycle is not regular and it recurs naturally at any frequency between once a year to less than once a decade.
This year around 2,500 tourist were fortunate to witness the event. The crowds cheered as the 97-square-mile glacier splintered and ice crashed down. The glacier first ruptured in 1917, taking with it an ancient forest of beech trees. The last rupture occurred two days ago in March 2, 2012, and previously in 2008. Altogether 21 ruptures has been recorded since 1917.
Picture taken in 2004, 2 weeks before the rupture of the glacier.
Large piece of ice colapses off of the edge of the Glacier Perito Moreno in Argentina in 2007.
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